It has been known in the past that magnets can be used to attract ferrous materials and thereby can separate ferrous particles from a random mixture of such particles with other nonferrous materials. This knowledge has been expanded to produce machines that can continuously effect such a separation from a continuously moving bed of particles containing some ferrous materials. Improved procedures have been developed to enhance the power of permanent magnets so as to provide a better separation of the magnetically attracted materials from the remaining materials that are unaffected by magnetic fields. See, for example, U.S. Pat. Nos. 2,992,736 to Buus et al.; 3,146,191 to Greenwald; 3,678,427 to Morgan; 3,737,822 to Buus et al.; 4,728,419 to Grun; and 4,869,811 to Wolanski et al.
It has now been found that a more powerful magnetic force can be produced by special arrangements of permanent magnets that are alloys of rare earths, especially samarium and neodymium, with iron and other elements. In particular, these arrangements of permanent magnets involve placing the magnets in parallel rows, each row extending across and under the moving bed of particles and separated from the next adjacent row by a thin strip of low carbon steel or other ferromagnetic material, with the magnet rows being positioned with the same polarity (N or S) touching the single separator strip between adjacent magnets. Thus the arrangement might be graphically shown as--N-Mag 1-S/st1/S-Mag 2-N/st1/N-Mag 3-S/st1/S-Mag 4-N/st1/--(where Mag-1=Magnet No. 1; Mag-2=Magnet No. 2, etc.; N=North, S=South, and St1=steel strip). This arrangement might present a cylindrical shape over which a belt moves supporting the particles to be separated. The details of the invention will be more fully described in the following text and in the drawings.